Process for distributing wax in cemented carbide powders



June 16, 1953 l L.. PoRGEs Erm. 2,642,230

PROCESS FOR DISTRIBTING WAX IN CEMENTED CARBIDE POWDERS Filed July 25, 194s Patented June V16, 1953 PROCESS Fon DISTRIBTINGWAX IN k v .Y CEMENTED CARBIDE POWDERS Leo Forges and Stanley T. Sawyer, London, Eng- Y land, assignors to A. Johnson Vda (London) Limited, Londonv, j England Company Application Jlyzs, 1949sr`ia1No; ishcc v InGreat Britain February 25,1948

This invention relates to the mixing, milling and lubricatingof finely divided metal powders and like pulverulent materials prior to pressing.

In the processing of metal powders it is usual, in currentl industrial practice, to place the constituent powders in a cylindrical container together with a suitable liquid such as distilled water, benzene, a-cetone or alcohol, whichliquid promotes mixing and milling and prevents oxidation of the metal powders during lmilling,

a number of balls being added to assist mixing and to increase the milling action. The container is sealed and fitted into a ball-milling machine and rotated for a Vcertain period, usually varying between 24 and'120 hours. The liquid is then evaporated from'the container and the' powder, when dry,.is separated-from the balls and subjected to heat treatment in aA reducing atmosphere to anneal the powder, since some powders become work-hardened durin'gwm'illing. To disperse a small quantity of substance s uch as a lubricantunifor'mly throughout the "metal powder the lubricant is dissolved in a'solvent' and then added to the powder, the liquid and the powder being mixed together in an fopen-panvlj "f mixing machine, during which operation the solvent evaporates. When the bulk of the solvent has evaporated, the powder is nally dried in a drying oven. By this process the lubricant is not evenly distributed throughout the charge, some layers tending to have far more lubricant thereon than other layers.

Attempts have been made to distribute a lubricant throughout a finely divided powder by placing the powder in a container, adding the lubricant dissolved in a solvent thereto, and subjecting the container to a rotary movement. Satisfactory distribution of the lubricant has not been obtained by this method. The lubricated powder has a tendency to cake on the walls of the container, and if there are balls therein the powder will also cake around these. Itmust be emphasized that in this process the -container is subjected to a rotatory movement.

According to the present invention there is provided a process for mixing and/or milling and uniformly distributing a comparatively small quantity of a substance throughout a nely divided material, wherein the finely divided material is placed in a container, and the substance which it is desired to distribute is dissolved in a solvent and added thereto, and wherein the container is subjected to a vibratorymovement so that mixing 'and/or milling take place, the solvent being removed by heating and/or by application of a negative pressure before the termi- 2 claims. (01.241415 f nation ot 'such vibratory mixing and/or milling. Y 1

Thel invention also includes any process containing the stepofplacing the finely divided ma- Vt'erial in a container and adding theV substance,

which it is desired to distribute, dissolved in a solvent thereto and then subjecting the container to a vibratory movement so that uniform distribution of the smallquantity of substance yitalics, place,vfthe solvent `being removed by heating and/or the applicationl of a negativepressure before the termination A*of suchvibratOry,

movement.

For a better understanding of the invention one mode of carrying it into effect will now be described with reference to the accompanying,` drawing, which shows a side-elevation, partly in Y section, of an appartus which may be employed for carrying out the invention.

The mixing, milling lubricating and solvent distillation'operations are carried out in a container Irnounted on supporting'plates 3, which are suspended by suspensionrods 4 from'the upper end of a framework 2, by angle-section sup- .porting members 5i Supported within the framework 2, is an `electric motor 6 which drivesan Y eccentrically mounted flywheel within a casing The casing 8 imparts a vibratory motion to the plates 3 andy 8 through a exible coupling 'I.

hence to the container I.

The container I is secured within an oil-jocket 9, the latter containing ,thermostatically controlled electric immersion heaters I 0 inserted through a sealing lid II. Additionally, the container I, has a ltightly fitting conical cover I2 with a flexible hose connection I3 which leads to a vacuum pump (not shown). In the use of this apparatus, balls are placed in the container I an-d cemented carbide powder, together with a required quantity of wax dissolved in benzene is added thereto.

period and towards the end of this period the oiljacket 9 is heated by the heaters I0, so that the solvent may be removed whilst the charge is still being vibrated. To accelerate the rate of evaporation and to reduce the possibility of oxidisation of the iinely divided metal powder during the heating period, the container is subjected to a negative pressure through the hose connection The removal of the solvent by heating is not effected until the mixing and milling operation is almost completed. It is very important that the powder charge should be in a violent state of The container I is then vibrated for a desired milling agitation whilst this distillation is taking place, so that the lubricant will be uniformly distributed throughout the charge. When dry the container is emptied andthe powder is separated from the balls, which are then returned to the apparatus.l

It is found that metal powders prepared b'yl the iinal product or for `a subsequent l. ,v

It is, of course,- known 4 ders, comprising the steps of placing finely divided cemented carbide powders in a container dissolving the wax which it is desired to dis! tribute in a solvent, adding the solution of said wax to said nely divided cemented carbide powders, grinding therpowders by subjecting the powders in said solution to a violent vibration and evaporating said solvent during said violent Vibration.

2. A process for mixing, milling and uniformly Y lubricating cemented carbide powders, comprising the lsteps of placing the cemented carbide powder in a container, dissolving wax in a solvent, adding the wax dissolved in the solvent to said cemented carbide powder, grinding the powders by subjecting the powders in said solution when it is so pressed cracks may develop therein It is also found that, with the product of the invention, in the subsequent-sintering process, even shrinkage of the product takes place in all three dimensions, thatxis, there is substantially an absence of distortion.' .This is because the lubricant has been evenly distributed through-k out the charge and the particles thereof are hence uniformly lubricated. The pressed product has also a much more uniform porosity because of the even distribution of ythe lubricant.

While the inventiorirhas been` Y application to the treatment of powder metals, it will be understoodV that-it is equally Aapplicable to a variety of other processes where it is desired to dispersel a small quantityoi a soluble solid body evenly throughout a comparatively large quantity of nely divided material, e. g. in Vthe manufacture of grinding wheelS.

Further it should be noted that this invention is specically suited tothe mixing Vand/or milling and iubricating of cementedcarbide powder mixtures for subsequent processinginto the'iinal sintered state. A

Weclaim:

l. A process for mixingniilling and uniformly distributing a comparatively small quantity of wax throughout finely divided cemented carbide powdesribed in its.,

Y' t@ ai. violent vibration and evaporating said s01 vent during said violent vibration.

LEO FORGES. .STANLEY r. SAWYER.

. Beterences Cited in the ille of thispatem;

UNITED STATES PAV-TENTS Number Name Darte 1,920,234 Arthur Aug. 1 1933 1,930,684 Kramer oet'. 1v 193s 2,002,891 Hau May 2s i935 2,272,629 Arthur heb. 101 i942 l FOREIGN PATENTS Number .Country Date 876.242 Great isritaia Janli, 1931 593.77? creat Britain ost. 24j', 194'? OTHER REFERENCES 

1. A PROCESS FOR MIXING, MILLING AND UNIFORMLY DISTRIBUTING A COMPARATIVELY SMALL QUANTITY OF WAX THROUGHOUT FINELY DIVIDED CEMENTED CARBIDE POWERS, COMPRISING THE STEPS OF PLACING FINELY DIVIDED CEMENTED CARBIDE POWDERS IN A CONTAINER, DISSOLVING THE WAX WHICH IT IS DESIRED TO DISTRIBUTE IN A SOLVENT, ADDING THE SOLUTION OF SAID WAX TO SAID FINELY DIVIDED CEMENTED CARBIDE POWDERS, GRINDING THE POWDERS BY SUBJECTING THE POWDERS IN SAID SOLUTION TO A VIOLENT VIBRATION AND EVAPORATING SAID SOLVENT DURING SAID VIOLENT VIBRATION. 